Engines may include crankcase ventilation systems to vent gases out of the crankcase and into an engine intake to provide continual evacuation of gases from inside the crankcase in order to reduce degradation of various engine components in the crankcase. Under certain conditions, crankcase ventilation systems may be monitored to identify breaches in the system. For example, a crankcase ventilation tube may become disconnected, an oil cap may be off or loose, a dipstick may be out of position, and/or other seals in the crankcase ventilation system may be broken resulting in degradation of various components included in the crankcase.
Various approaches may be used to monitor crankcase ventilation system integrity. For example, a pressure sensor may be used in the crankcase and a valve in a crankcase vent tube may be opened so that pressure or vacuum changes may be sensed in the crankcase to determine if there is a breach in the system.
In other approaches, a plurality of absolute sensors, e.g., a barometric pressure sensor (BP), a compressor inlet pressure sensor (CIP), a throttle inlet pressure sensor (TIP), a manifold air pressure sensor (MAP), and/or a pressure sensor in a crankcase vent hose, etc., may be used in combination to monitor crankcase ventilation system integrity.
However, the inventors herein have recognized that such approaches may add additional hardware to such monitoring systems, e.g., additional sensors and valves, thus increasing costs and complexity of a crankcase ventilation monitoring system. Additionally, some of these sensors may be underutilized, e.g., the crankcase pressure sensor may only be used for crankcase breach detection, thus limiting the value of such sensors.
Thus, in one approach, to at least partially address these issues, an engine method is provided. The method comprises indicating crankcase ventilation tube degradation based on humidity. In this way, a crankcase ventilation tube connection may be indicated by a humidity sensor that is available to also provide information to other vehicle and/or engine systems.
In one example, the humidity may be determined from a humidity sensor placed in the crankcase ventilation tube. The sensed humidity may change depending on engine boosting. For example, when an intake manifold pressure is less than a barometric pressure (not boosted) the humidity sensor may read ambient humidity. Ambient humidity information may then be used to adjust engine operating parameters. In another example, when the intake manifold pressure is greater than barometric pressure (boosted), the humidity sensor may read a humidity value greater than ambient humidity when the crankcase ventilation tube is connected. Under the same conditions, the humidity sensor may read a lower humidity value (e.g., ambient humidity) when the crankcase ventilation tube is disconnected. In this way, degradation of the crankcase ventilation tube may be diagnosed based on sensed humidity and engine boosting.
Further, a humidity sensor in the crankcase ventilation tube may be used to diagnose the functionality of the humidity sensor and determine an estimation of a blowby rate. For example, if the humidity sensor's reading does not change under boosted and non-boosted engine operation, the sensor may be degraded. In another example, the rate of humidity climb when an intake manifold pressure increases from below barometric pressure to above barometric pressure may approximate a blowby rate. As such, a higher rate of humidity increase and higher blowby rate may indicate increased engine degradation.
In this way, a humidity sensor placed in the crankcase ventilation tube may provide diagnosis of engine health. The humidity sensor may also provide ambient humidity data, during selected conditions, in order to control other engine systems, along with diagnosing the proper functioning of the humidity sensor. Finally, the humidity sensor may provide an indication of crankcase ventilation tube disconnection.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.